In this April 8, 2008, photo provided by the Iranian President’s Office, Iranian President Mahmoud Ahmadinejad, center, visits the Natanz Uranium Enrichment Facility about 200 miles south of the capital Tehran.

VIENNA — Iran is on the threshold of being able to create weapons-grade uranium at a plant it has heavily fortified against Israeli attack, diplomats told The Associated Press on Thursday, calling into question an Israeli claim that Iran had slowed its nuclear timetable.

One of three diplomats who discussed the issue said Iran was now technically ready within days to ramp up its production of 20 percent enriched uranium at its Fordo facility by nearly 700 centrifuges. That would double present output, and cut in half the time it would take to acquire enough of the substance needed to make a nuclear weapon, reducing it to just over three months.

Such a move would raise the stakes for Israel, which has said it believes the world has until next summer to stop Iran before it can get nuclear material and implied it would have time to decide whether to strike Fordo and other Iranian nuclear facilities.

The two other diplomats who spoke to the AP could not confirm the 700 number. But both agreed that Tehran over the past few months had put a sizeable number of centrifuges at Fordo under vacuum. It takes only a few days to begin enrichment with machines that are under vacuum.

While experts agree that the Islamic Republic could assemble enough weapons-grade uranium to arm a nuclear weapon relatively quickly, they point out that this is only one of a series of steps need to create a working weapon. They say that Tehran is believed to be years away from mastering the technology to manufacture a fully operational warhead.

All three diplomats are from member nations of the IAEA, which is scheduled to release its latest report on Iran’s nuclear program as early as Friday. They demanded anonymity because they were not authorized to discuss restricted information with reporters.

Israeli Defense Minister Ehud Barak’s assertion earlier this month that Iran has “essentially delayed their arrival at the red line by eight months,” is in line with the timeframe laid out by Israeli Prime Minister Benjamin Netanyahu in September, when he spoke at the U.N. General Assembly.

IAEA officials said they would have no comment. A phone call to Ali Asghar Soltanieh, Iran’s IAEA representative, went to voicemail.

Based on intelligence from the United States and other IAEA member nations as well as its own research, the agency suspects that Tehran has done secret work on developing nuclear weapons. Washington and its allies also fear that Iran is enriching uranium to reach the ability to make such arms. But Tehran denies any interest in atomic arms, dismisses allegations that it has conducted weapons experiments and insists it is enriching only to make nuclear fuel and for research.

In Washington, President Barack Obama told reporters there is still time for the United States and Iran to reach agreement on Iran’s nuclear program.

Obama said there should be a way for Iran to enjoy “peaceful nuclear power” while still meeting international obligations and providing assurances that they are not developing nuclear weapons.

The Vienna-based IAEA, in its last report in August, said that Tehran had doubled the number of centrifuges at Fordo within three months to more than 2,000. Diplomats since then have told reporters that hundreds more have been installed, bringing the total to nearly 2,800, or full capacity for Fordo. But the number operating — about 700 — has not changed from early this year.

Iran has a far larger enrichment plant at Natanz, in central Iran, which churns out uranium enriched below 4 percent. But the 20-percent material being produced at Fordo is of greater concern to the international community because it can be turned into weapons-grade uranium of 90 percent purity much more simply and quickly — and because the facility, near the holy city of Qom, is well protected against attack.

Barak’s comments appeared prompted by the IAEA’s August report, which said Iran had turned much of its 20-percent uranium into reactor fuel plates that are difficult to retool into warhead material. As a result, it is still far short of the amount of more highly enriched uranium it would need to progress to weapons-grade levels.

But depending on how many more centrifuges it activates, it could quickly replace the converted material and reach the 140 kilograms — about 300 pounds — needed for at least one warhead.

Tehran “should be in a position to produce enough (material) for two or three” nuclear warheads by the summer, if does decide to double output in the next few weeks, said Olli Heinonen, the International Atomic Energy Agency’s deputy director general in charge of the Iran file until 2010.